When $\mathrm{SO}_{2}$ is passed through acidified $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{0}$, the process…
When $\mathrm{SO}_{2}$ is passed through acidified $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{0}$, the process that takes place is
the solution turns blue
the solution is decolourised
$\mathrm{SO}_{2}$ is reduced
green $\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}$ is formed
Solution
When $\mathrm{SO}_{2}$ is passed through acidified $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ solution. $\mathrm{SO}_{2}$ gas turns acidified potassium dichromate solution from orange to green reduced chromium $+4$ to $+3$.
$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}+2 \mathrm{H}_{2} \mathrm{SO}_{4}+3 \mathrm{SO}_{2} \rightarrow 2 \mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}+\mathrm{K}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}$